Stampings and progressive stampings are used to manufacture parts and pieces of many different types and shapes for use in a variety of different assemblies and constructions. Metal can be shaped into many different forms and configurations by the application of force causing a metal blank to conform to the shape of a die used while applying the force. Simple parts and pieces can be made by a single stamping. In a single stamping, force is applied in a single event so that the metal conforms to a die used while applying the force. For more complex parts or parts taking a shape quite different from the original metal blank, progressive stampings are used. In progressive stampings, a series of dies are used in a series of stamping events, with each die and each stamping event forming the metal in stages from the original blank to the desired final formation.
It is known to use stamping techniques to form a variety of parts having an expanded area or flare at an end thereof. For example, a substantially cylindrical or tubular part can be stamped to have an outwardly bulged or flared portion at one end thereof. The initial flaring process can be a precursor, or preliminary step to a subsequent operation. By way of example, it is known to flare a tube end and then compress the flared portion in a folding manner onto itself to produce a two layer thick foot or flange at the end of tube.
Stamping is often used to make parts and pieces inexpensively, since a stamping event is a rapid occurrence. Accordingly, parts can be formed quickly and inexpensively, with minimal waste. To ensure a high percentage of quality parts are shipped to customers cost effectively, testing procedures for stamped parts must be performed rapidly and reliably. Preferably, a testing method occurs quickly so that testing or inspection of the part does not slow the overall process of making the part.
When forming expanded portions of stamped components, such as flared ends on tubes or pipes, the material in the portion being expanded or flared can crack. It is important to identify cracked parts as the crack can cause leakage if the part is configured for conducting fluid flow therethrough, and a crack in the part can propagate, leading to premature failure of the finished part. A cracked flared end formed in a preliminary step, in anticipation of forming a folded flange as described previously, can lead to a defective finished part. If load-bearing, the part may be inadequate causing a joint to fail due to providing insufficient bearing area for an installed assembly causing loss of clamp load. The part also can be mal-formed if cracks are present from earlier steps.
Detecting a flaw such as a crack can be difficult. Known stamping defect detection systems evaluate changes in forming pressure to detect defects. Small cracks may not be sufficient for detection at the time; however, due to propagation small cracks may be significant later. After the part is completed defect detection also may be difficult. For example, on a part having a folded flange or foot that looks acceptable, the crack or cracks may be hidden beneath the folded material and therefore difficult to detect after the part is completed.
It is desirable to identify parts in which defects have occurred so that the defective part is not shipped together with acceptable parts. Since many parts made by stamping that include expanded or flared components are produced quite rapidly at low cost, it is desirable that any apparatus and process for identifying cracked parts or components work equally fast so as not to slow the manufacturing process, or add undue cost to the final price of the part being produced.
What is needed in the art is a crack testing apparatus that quickly and accurately identifies cracked parts such as a crack in a flared end of a tube, pipe or the like.